Tilt-wing Aircraft Research Articles

Aerodynamic blade design with multi-objective optimization for a tiltrotor aircraft

Purpose – The purpose of this paper is to present the aerodynamic blade design of a tiltwing aircraft with a multi-objective optimization procedure. The aerodynamic design of tiltrotor blades is a very challenging task in the project of this type of aircraft. Design/methodology/approach – Tiltrotor blades have to give good performance both in helicopter and aeroplane modes. According to the design parameters (the chords, the twists and the airfoils along the blade), as the optimization objectives are different from one operating condition to another, the blade is the result of a multi-objective constrained optimization based on a controlled elitist genetic algorithm founded on the NSGA-II algorithm. The optimization process uses a BEMT solver to compute rotor performance. To avoid negative effects due to compressibility losses in aeroplane mode, the blade shape has been refined following the normal Mach number criterion. Findings – It has been found that the optimized rotor blade gives good performance bo...

Flight control law design criteria for the transition phase for a tiltwing aircraft using multi-objective parameter synthesis

Aircraft in tiltwing configuration combine the advantages of helicopters, such as hovering and vertical take-off and landing capabilities (VTOL), with the advantages of conventional fixed-wing aircraft, in particular long endurance and economic flight at higher velocities. During the transition phase between hovering and aerodynamic horizontal forward flight the aerodynamic forces and moments, the direct forces due to propulsion system and propulsion-induced aerodynamic forces and moments have to be properly balanced. Tilting the wing from vertical to horizontal position (and vice versa) poses a significant change in configuration. In combination with the given large velocity range this influences the control device efficiency significantly. At the same time, the tilting of the wing provides an additional control parameter. During flight control law design for an unmanned tiltwing aircraft with focus on the transition phase multi-objective parameter analysis and synthesis provides a powerful means to identify interdependencies and sensitivities. Key aspects of the longitudinal motion during the transition phase are investigated in this study using the multi-objective parameter synthesis tool MOPS, developed by the DLR Institute of System Dynamics and Control. Aim of this paper is to analyze quality criteria with respect to design and evaluation of control laws during transition phase. To achieve these parameters forward velocity and pitch attitude controller are optimized with respect to control and disturbance responses. At the same time the overall robustness against selected uncertain model parameters, such as actuator dynamics is considered explicitly. Different quality criteria characterizing these motions are developed and discussed in detail.

Advances in rotorcraft

Reviews recent advances in rotorcraft technology as presented at a recent Royal Aeronautical Society conference on innovation in rotorcraft technology and the 1997 Paris Air Show. Reports research initiatives to improve key rotorcraft technologies in the areas of obstacle detection, vibration and noise reduction and smart structures. Also mentions advances in overcoming rotorcraft speed limitations through use of tiltrotor and tiltwing aircraft.

Sizing methodology for reaction-driven, stopped-rotor vertical takeoff and landing concepts

Reaction-driven, stopped-rotor, vertical takeoff and landing (VTOL) aircraft concepts offer great potential for application by allowing the use of a common propulsion system for high-speed cruise and low-speed powered lift. Using the rotor for lift in both flight modes increases its utility. Existing analysis and design methodology for shaft-driven VTOL concepts, like helicopters or tilt-rotor and tilt-wing aircraft, cannot be applied to reactiondriven, stopped-rotor concepts. The methodology for sizing this type of vehicle is presented, addressing both internal gasdynamics and external aerodynamics, along with consideration of their noncomplimentary interactions. Aerodynamic compromises required to obtain flight in both fixed- and rotary-wing modes are presented. Lessons about design issues and tradeoffs learned during the development of this methodology and its implementation are discussed. Finally, the results of applying this methodology to an example of this type of vehicle, the canard rotor/wing, show its utility.

Review of V/STOL Aircraft with Tilt-Propellers and Tilt-Rotors

SummaryTests of the first experimental VTOL aircraft using tiltable wings and propellers indicated that practical operational aircraft are possible and can operate with a high degree of effectiveness.The flight tests accomplished up to the present time with the second generation tilt-propeller and tilt-rotor aircraft are discussed and analysed. The XC-142 and the CL-84 tilt-wing aircraft have been performing well throughout their projected flight envelope and good pilot ratings have been obtained with each in hover, transition, and the normal cruise mode. The X-19 tandem wing tilt propeller was flown only up to 100 knots and was lost due to a structural failure in one nacelle. Although the operation of the aircraft had been satisfactory up to this point, this programme was terminated due to shortage of funds.A study of the various VTOL aircraft configurations operating at low radius of action indicates that the tilt wing/ tilt propeller type are the most cost-effective as long as speed is an important parameter in the operating mission. There are missions where speed is of secondary importance, and therefore, the helicopter will continue to be one of the most effective VTOL for these missions.Since the tilt-wing /tilt-rotor aircraft tend to be only slightly higher in cost than the helicopter and with development the complexity and maintainability will be reduced to acceptable levels, it is anticipated that further work will be done in the development of these vehicles, and successful and useful machines will be built in the future.

Development of the Tilt-Wing Aircraft

The author accepted the invitation to present this paper on the rash assumption that he would be able to present something new and useful on the tilt-wing. The Hiller Company (in partnership with Vought and Ryan) was the first to have received a fully-fledged development contract for evaluation quantities of any VTOL machine. The VHR-447 which was selected as the Army, Navy and Air Force XC-142A was a culmination of almost ten years of effort spent in the investigation and promotion of the tilt-wing “propello-plane” VTOL aircraft concept.

Tilt Wing Aircraft in comparison with other VTOL and STOL Systems

The CHAIRMAN, in introducing the Author, said that although it had in the past been the main concern of the Association to discuss the problems of the conventional helicopter, it was now proposed to include systems allied to it, and convertiplanes and other powered lift systems would be considered at this and future meetings of the Association There was now a whole spectrum of proposed direct lift aircraft ranging from the conventional helicopter of a few pounds per sq ft disc loading, to jet lift aircraft of hundreds of pounds per sq ft of jet area Between these two extremes there was a variety of convertiplanes and jet wing systemsThe Author had been working on rotorcraft for a long time He had been Chief Aerodynamicist of the Vertol Aircraft Corporation and Director of Aeronautical Research there, he had written many papers relating to the helicopter especially on aerodynamics, and his books on the subject published by the Rotorcraft Publishing Committee had been very widely read, even on this side of the Atlantic